MGF

What it is

MGF is the message a muscle sends itself after you load or damage it: wake up the satellite cells and start repairing. Injected into a muscle right after training, it is used to bring up a lagging body part or speed recovery of a strained one. It acts where you put it, for minutes, which is both the point and the limitation.

The people who use it are lifters with a body part that will not grow in proportion, athletes rehabbing a muscle strain who want the repair signal concentrated in the damaged tissue, and older trainees whose own MGF response to training has faded. It is the local counterpart to IGF-1 LR3: where LR3 is a systemic growth signal, MGF is site-specific and short-lived. It is not a mass builder, it does nothing if you do not train the muscle, and it is the wrong tool if you want body-wide growth.

What people notice is a stronger pump and fuller feel in the injected muscle within a few sessions, less soreness and faster readiness to train it again, and, over 8 to 12 weeks, a lagging muscle catching up a little. The gains are modest and local. If the muscle is not visibly different after 12 weeks of hard training with MGF, the peptide is not the missing piece.

Doses are 100 mcg to start, 200 mcg standard and 300 mcg at most, injected IM into the muscle you just trained, within about 30 minutes of finishing, on training days only. A 5 mg vial in 1 ml is 5 mg/ml, so 200 mcg is 4 units on an insulin syringe; split it between the two sides for a bilateral muscle. Runs are 8 to 12 weeks, then a few weeks off; there is no sign it stops working, but there is no human data at all on longer runs, so the break is caution. A 5 mg vial is 25 doses at 200 mcg, about 8 weeks at three sessions a week, so one vial is roughly one run. The classic mistakes are injecting it subQ in the belly, which wastes a local signal, dosing it on rest days, and megadosing, where more does nothing for a peptide that is cleared in minutes.

The evidence is cell and animal biology, and it is real: MGF (the IGF-1Ec splice variant) is produced by muscle after loading, activates satellite cells and drives repair in rodent models, and the response fades with age. There is no human trial of injected MGF for muscle, bone or anything else. It is not approved, and it is a product you buy on the quality of the vendor's testing. For a peptide used for its local effect, that is the honest ceiling on expectations.

If you want a systemic growth signal, IGF-1 LR3 is the stronger compound, with its own cautions. If you want MGF's effect without the post-workout timing window, PEG-MGF is the long-acting version dosed two to three times a week. Skip MGF if you have had cancer, since it is an IGF-1 family growth signal, and skip it if you train a body part once a week and hope the peptide makes up for it.

What people use it for

Safety, in brief

The full picture — stop signs and who should talk to a doctor first — is on the dosing guide.

Sources

The labels and studies behind this page. Each link opens the original on PubMed, DailyMed or ClinicalTrials.gov.

1. Different roles of the IGF-I Ec peptide (MGF) and mature IGF-I in myoblast proliferation and differentiationYang et al., FEBS Lett 2002 · Study
2. Mechano Growth Factor E peptide (MGF-E), derived from an isoform of IGF-1, activates human muscle progenitor cells and induces an increase in their fusion potential at different agesKandalla et al., Mech Ageing Dev 2011 · Study
3. Mechano growth factor E peptide promotes osteoblasts proliferation and bone-defect healing in rabbitsDeng et al., Int Orthop 2011 · Study
4. Mechano growth factor, a splice variant of IGF-1, promotes neurogenesis in the aging mouse brainTang et al., Mol Brain 2017 · Study